The discount 4 Layers PCB Board is an electronic card, usually green in color, that provides four conductive layers to route electronic signals. 4 layers PCB Board refers to the printed circuit board is made of 4 layers of glass fiber. There are four wiring layers: Top layer, bottom layer, VCC, and GND. Generally, through holes, buried holes, and blind holes are used to connect the layers. There are more buried and blind holes than double-side boards. In addition, try not to run signal track on the two layers of VCC and GND.